MAKHACHKALA, Russia – Russian authorities say one person has been killed and three others detained in an operation to break up a sleeper cell of the Islamic State in the country's restive southern region of Dagestan.

The National Anti-terrorism Committee said the operation took place Sunday in the city of Derbent, on the Caspian Sea near the border with Azerbaijan.

The committee said in a statement that one militant was killed by police after they blockaded his house and he opened fire. Three others were arrested at other locations.

Mainly Muslim Dagestan is the principal breeding ground for Islamic militants in Russia, and the regions sees regular attacks on Russian police and officials. Russia fought two separatist wars in the neighboring province of Chechnya after the 1991 fall of the Soviet Union.